1. Field of the Invention
The present invention relates to a skin-whitening agent, in particular, to a novel skin-whitening agent which is not intended to inhibit the function and activity of tyrosinase, but intended to suppress the formation of tyrosinase, i.e. suppressing melanogenesis by preventing the formation of tyrosinase per se.
2. Description of the Prior Art
Melanin, which usually occurs in the skin, plays an important role in the protection of the human body from ultra-violet rays, as well as being very important as a medical and cosmetical factor. Melanin is synthesized by tyrosinase in dermal pigment cell through the convertion of tyrosine into dopa, dopa quinone and 5,6-dyhydroxiindole in the given order. Excessive pigmentation may result in dark skin, and its local occurrence may lead to chloasma or freckle, which are all cosmetically defective.
Conventionally, hydroquinone and MBEH (monobenzylether of hydroquinone) have been used to realize beautiful clear skin: These compounds bear a strong skin-whitening ability which is however mainly due to denaturation and death of pigment cell. Thus, the use of these compounds may damage dermal physiology to elicit undesirable side effects such as irreversible leukoderma, pigmentary disorder and contact dermatitis.
In view of the foregoing, Japanese Patent Kokai 53-142515 first highlighted tyrosinase as a factor which is responsible for melanogenesis, as well as proposing the use of vitamin C, glutathione and cysteine in order to reduce dermal melanin for the realization of beautiful clear skin.
Each of these compounds however acts as a tyrosinase inhibitor which inhibits the activity and function of a tyrosinase which has been formed. As mentioned above, prior art has been focused on the way of inhibiting the activity of tyrosinase.
While the skin-whitening agent of this invention is intended to prevent the formation of tyrosinase, but unlike prior art not concerns the way of treating formed tyrosinase. In other words, we draw attention to tyrosinase which is the root cause of cosmetical troubles, and the skin-whitening agent of this invention is directed to the most fundamental part of the melanogenic system, i.e. suppressing the formation of tyrosinase.
Since such a skin-whitening agent has never proposed, this technical object is deemed to be novel. To attain such a novel object, this invention employs as the effective component at least one member selected from lactic acid, lactates of alkali metal or alkaline earth metal, and nonmetallic derivatives of lactic acid at a concentration of 5 w/w % or higher optionally with an unsaturated fatty acid. Prior art teaches and discloses nothing about this technical concept. The skin-whitening agent of this invention is therefore entirely novel.
For this reason, this invention is novel in object and elements, and the advantage is therefore novel and remarkable.